OPI (version 1.6)

opiTemporalStimulus: Stimulus parameter list.

Description

List containing stimulus parameters with an S3 class attribute of opiTemporalStimulus.

Details

• xcoordinate of the center of stimulus in degrees relative to fixation
• ycoordinate of the center of stimulus in degrees relative to fixation
• imagean image to display in a machine specific format
• lutifis.na(image)then this is a lookup table (vector) for stimulus level at each step of rate Hz in cd/$\mbox{m}^2$. If image is specified, then this is a list of images, in the same format as image, that is stepped through at rate Hz.
• sizediameter of target in degrees, or scaling factor for image if specified
• colormachine specific stimulus color settings (ignored if!is.na(image))
• ratefrequency with which lut is processed in Hz
• durationtotal length of stimulus flash in milliseconds. There is no guarantee thatduration %% length(lut)/rate == 0. That is, the onus is on the user to ensure the duration is a multiple of the period of the stimuli.
• responseWindowmaximum time (>= 0) in milliseconds to wait for a response from the onset of the stimulus presentation
• ...machine specific parameters

Octopus 900{ x and y are in degrees, with precision to one decimal place recognised.

image is not possible on an Octopus 900.

lut is not possible on an Octopus 900. Stimulus is at 0 dB.

rate is in Hz, with precision to one decimal place recognised.

color is ignored. Use opiSetBackground() to alter stimulus color. }

References

Please cite: A. Turpin, P.H. Artes and A.M. McKendrick "The Open Perimetry Interface: An enabling tool for clinical visual psychophysics", Journal of Vision 12(11) 2012.

http://perimetry.org/OPI

Examples

# A Size III flickering with a 10Hz square wave at
    # location (7,7) with luminance 10 dB (HFA) 
stim <- list(x=7, y=7, size=0.43, color="white", 
                rate=20,        # one lut step per 50 ms 
                lut=c(0,318),   # so one full lut per 100 ms == 10Hz 
                duration=400,   # and 4 cycles per stimulus
                responseWindow=1500) 
class(stim) <- "opiTemporalStimulus"